The invention starts out from a rotating piston machine, which can operate as a pump, a compressor or an engine. In the case of a known rotating piston machine of the generic type (German patent 42 41 320, European patent 1,005,604), a high leakproofness between the working chambers is aimed for also by means of the configuration of the teeth, in order to keep the leakage as small as possible from one working chamber to the adjacent working chamber over the flanks with line contact between driving a driving rotor and a driven rotor and vice versa. In this connection, the crests of the tooth of one rotor proceed linearly at the flanks of the other rotor, the course of the working surface of which is cycloidal.
The output, required from such a rotating piston machine, varies depending on the use, to which it is put. For this purpose, different control and regulating methods are known. The simplest method is to combine the pressure and suction sides of the machine. However, with regard to the high energy taken up by the machine, this makes hardly any difference. In many cases, especially when used as a lubricating pump in the motor vehicle sector, but also when used as a presupply pump for a diesel fuel injection system, every effort is made to keep the energy, taken up by the machine, as low as possible and to adapt it to the actual power output (see German Offenlegungsschrift 100 25 723).
In comparison to the above, the inventive rotating piston machine with the characterizing distinguishing features described herein has the advantage that the energy, taken up by the rotating piston machine, corresponds directly to the power output of the same. A leakage loss of such a machine, which can never be avoided completely, has become a quantity control or loss quantity control, which is brought about by a selective change in the gap width. A further advantage consists therein that foaming, which may arise, for example, when controlling the return channel, is largely prevented, for example, when fuel or oil is pumped.
It is known that, by connecting the suction side with the pressure side directly (DE 100 25 723), a corresponding decrease in energy uptake can be achieved in fuel pumps. However, such systems do not involve working chambers located on the front faces of the rotors and, instead, are concerned with gear pumps with radially disposed cogs or annular gears with a completely different mode of operation from the very start (displacement in the axial direction), so that such variously known solutions cannot be used for the invention. Accordingly, for an oil pump, which also works with a gear wheel and an annular gear, it is known (U.S. Pat. No. 5,085,187) that the pump working chambers may be closed off laterally by a lid, which is shifted when the pumping pressure is sufficiently high, so that a connection is established between the suction space and the pressure space of the oil pump.
For adapting the energy uptake to the actual power output of rotating piston machines with gearing at the front (U.S. Pat. No. 2,049,775), it is known that the driven rotor may be swiveled within a spherical bearing, in order to change the axial angle between the axes of rotation by these means, which may lead correspondingly to a change in the amount pumped up to a zero amount pumped. It is a disadvantage of such a construction that the costs of construction are considerably higher and the output capability is more limited. Moreover, above all, the sealing of the working chambers from the adjusting device is a disadvantage.
Additionally, a media delivery assembly is known from DE 103 35 939 A1, comprising a driving rotor and a driven rotor driven by the driving rotor, which are rotatably mounted in a rotor housing and interact by meshing with each other by way of spur gears, wherein at least one of the rotors can be axially adjusted and, to the rear thereof, facing away from the other rotor, a compensating pressure can be applied by way of a compensating channel. The compensating pressure both acts counter to the axial pressure forces developing in the working chambers that are formed between the rotors, and compensates for forces that would push the two rotors apart. This ensures that the distance between the rotors does not change. The compensating pressure often corresponds to the pressure of the pressure side of the delivery assembly, and thus necessitates considerably higher forces on the rotors. This produces increased friction in the bearings and between the rotors. Supply can also be made to the back of the rotor by way of gap flows. This is disadvantageous in that an undefined compensating pressure develops, which is dependent on the leakage flows flowing into the space, or out of the space, behind the rotor. In this embodiment as well, the amount of compensating pressure is not ideal for low-friction operation.